Double acting slips

ABSTRACT

A unitary, double acting slip is disclosed having a first surface adapted to fit against the wall of a cylindrical member, such as a pipe, and a second surface adapted to be forced against the adjacent surface of a bowl member so that the slip is wedged between the cylindrical member and the bowl after limited movement of the pipe. The second surface of the double acting slip has a thicker section intermediate its length and tapers from the thickest section to the ends of the slip thereby forming two tapered wedging areas. The second surface of the double acting slip may include a recess and the bowl may have a radial opening extending to the slip. A bearing member may be resiliently mounted in this opening to engage the recess in the second surface of the slip in order to aid in alignment of the slip.

United States Patent Hayes, Jr.

[ June 20, 1972 Thomas J. Hayes, Jr., Houston, Tex.

[52] U.S. Cl ..24/263 DA, 24/249 DP [51] Int. Cl ..E2lb 19/06 [58] Field of Search ..24/263.5, 249 DP; 254/295 [56] References Cited UNITED STATES PATENTS 1,604,580 10/1926 .laques ..24/263.5 T UX I 2,229,607 1/1941 Poist et al. ..24/263.5 L 2,328,033 8/1943 Schorer ..254/29.5 UX 2,352,370 6/1944 Carruthers.... .....24/263.5 DA UX 2,841,961 7/1958 Lucas ..24/263.5 A X 2,340,597 2/1944 Kelley ..24/263.5 SB

Primary ExaminerDonald A. Grifiin' Attorney-Hyer, Eickenroht, Thompson & Turner [57] ABSTRACT A unitary, double acting slip is disclosed having a first surface adapted to fit against the wall of a cylindrical member, such as a pipe, and a second surface adapted to be forced against the adjacent surface of a bowl member so that the slip is wedged between the cylindrical member and the bowl after limited movement of the pipe. The second surface of the double acting slip has a thicker section intermediate its length and tapers from the thickest section to the ends of the slip thereby forming two tapered wedging areas. The second surface of the double acting slip may include a recess and the bowl may have a radial opening extending to the slip. A bearing member may be resiliently mounted in this opening to engage the recess in the second surface of the slip in order to aid in alignment of the slip.

11 Claims, 7 Drawing Figures PATENTEDmzo m2 3. 670,374 sum 1 or 3 NVENTOR. THOMAS .1 HA YES, J/e.

PKTENTEDJUMO m2 3,579, 374

sum 20F 21 A f q a 'Z\ Wm r A i? wrana: i i a 7- I 3 N I. THOMAS J. HA YES, JR. INVENTOR.

BY H 9M I m 4- TW V ATTORNE Y5 DOUBLE ACTING SLIPS This invention relates to improvements in slips for releasably holding cylindrical members such as pipes, and in one of its aspects to a unitary, double acting slip for holding the pipe against movement in either direction along'its length. In another aspect the invention relates to such a double acting slip which may be used in a hydraulic press.

Generally slips are wedged between a pipe and a slip receiving bowl and act to hold the pipe in one direction only. In such slips the wedging surfaces of the slips are tapered only in one direction, and in order to limit movement of the pipe in both axial directions, two slips have generally been employed. In this instance each slip is oppositely tapered and one is employed for holding in each direction, thus requiring the handling of two separate slips and manually or otherwise placing them in position each time the direction of movement of the pipe changes.

In one prior slip a unitary slip segment is used to retard movement of the pipe in either axial direction. In this slip the wedging surface is concave, tapering from the thickest section at the ends of the slip to the thinnest section intermediate the length of the slip. The bowl member which the slip is wedged against in response to movement of the pipe is the complement of the wedging surface of the slip so that movement of the pipe in either direction will cause one end or the other of the slip to become wedged between the bowl and the pipe. However, slips having this configuration produce the largest stress at points at or near the ends of the slip. The wedging forces radially directed against the pipe at these points adjacen't the ends. of the slip are so large that the pipe is frequently deformed or crushed.

It is thus an object of this invention to provide a unitary, double acting slip in which the holding forces applied to a cylindrical member, such as a pipe, are distributed over a greater area of the pipe than by previously used such slips.

It is another object of this invention to provide such a slip which applies the largest radial forces against the pipe in an area away from the ends of the slip and intermediate the ends of the slip. Another object is to provide such a slip which is simple and easily manufactured.

Also, it is desirable that when the wedging forces of the slips are relieved and the pipe removed from them that the slips automatically return to their position in the bowl prior to application of such forces. It is thus another object of this invention to provide a unitary, double acting slip assembly including a bowl member and a double acting slip having means for so automatically aligning themselves to a predetermined position after the slip has been displaced.

A further object of this invention is to provide such a slip which is particularly useful for releasably holding pipe in a hydraulic press.

These and other objects are accomplished in accordance with the illustrated embodiment of the invention by a double FIG. 2 is a sectional view of the slip and bowl assembly taken at 2-2' of FIG. 1.

FIGS. 3A, 3B, 3C are longitudinally sectioned views of the slips taken at 3-3 of FIG. 2.

FIG. 4 is a top profile view of the two slip segments mounted in the lower portion of the bowl.

FIG. 5 shows the detail of the teeth used to frictionally engage a pipe.

Referring to FIG. 1, a hydraulic press, indicated in its entirety by reference number 10, is shown as including a frame 13 on which is mounted a fixed pipe support member 11, a movable pipe support member 12, and double acting hydraulic cylinders 14. Hydraulic cylinders 14 are connected between support members 11 and 12 for causing relative movement of support member 12 with respect to support member 11. Each of support members 11 and 12 includes a double acting slip which is indicated by reference numbers 30 and 31, respectively. Hydraulic press may be used to join a length of pipe (not shown) held in slip to a pipe 90 held in slip 31 shown in FIGS. 3A, 3B and 3C by forcing one pipe to telescope into the other pipe to form a joint. Hydraulic press 10 may also be used to insert a mandrel into an'end of one of the pipes to expand this end and form a bell into which the second pipe may be inserted. Hydraulic press 10, utilizing the slips of this invention, has particular application to forming the pipe joint and practicing the method thereof disclosed in v US. Pat. Nos. 3,208,136 and 3,210,102. Slips 30 and 31 are acting slip having a first surface for frictionally engaging a cylindrical member, such as a pipe, and a second surface for cooperation with a bowl. The second surface of the double acting slip is tapered from a thicker section intermediate the slip to the ends of the slip. The second surface abuts against the substantially complementing face of the bowl when an axial force has been applied to the pipe so that the slip is wedged between the pipe and the face of the bowl to prevent any further movement of the pipe.

In accordance'with a further novel aspect of the invention, the second surface of the slip has a recess in its thickest section for receiving a bearing member located in a radial passage in the bowl. The bearing member, which may be a spherical ball, is maintained within the recess in the second surface of the slip by means of a spring which applies a radially directed force to urge the ball into the recess.

In the drawings where there is shown, by way of illustration, one embodiment of the invention:

FIG. 1 is a perspective view of a hydraulic press assembly utilizing the slips of this invention.

used in press 10 to limit the movement of the pipes when they are subjected to the tremendous axial forces necessary to form the joint.

As shown in FIG. 1, hydraulic cylinders 14 each include a piston rod 15 and a cylinder housing 16. Housing 16 includes lug 16a and support member 11 includes ears 11a, and lugs 16a are connected by pins 17 to ears 11a of support member 11. Piston rod 15 includes a lug 15a and support member 12 includes ears 12a, and lugs 15a are connected to support member 12 by pins 18.

Referring to FIGS. 1 and 2, each pipe support member 11 and 12 includes an upper slip receiving bowl l9 and a lower slip receiving bowl 20, each having a groove 19a and 20a, respectively to receive slips 30 and 31. Upper bowl 19 is pivotally mounted upon lower bowl 20 by means of pins 21 and closes down on lower bowl 20 so that the grooves 19a and 20a are adjacent to each other and form an opening for receipt of the slips and the pipe to be held. When the pipe is placed on slips 30 or 31 upper bowl 19 is tightened against the pipe housed in the bowls by a screw clamp 22.

Slips 30 and 31 preferably include a plurality of segments; for example, in the embodiment shown in FIGS. 1 and 2, slip 30 is comprised of four segments 30a, 30b, 30c, and 30d, and slip 31 includes segments 31a, 31b, 31c, and 31d. Segments 30a and 30b and 31a and 31b are mounted in grooves 19a and segments 30c and 30d and 31c and 31d are mounted respectively in grooves 20a and are held in place by plates 80. Each of segments 30a-30d and 3la-31d includes a first pipe engaging surface 32 to frictionally engage the wall of the pipe upon the application of pressure from tightening of clamp 22 and from the wedging action of the slip, which will be described below, in order to limit relative movement between the slip and the pipe along the length of the pipe. First surface 32 is preferably threaded or includes teeth 32a as shown in FIG. 5 in order to increase the coefficient of friction between 1 surface 32 and the wall of the pipe as the slip is wedged between the bowl and the wall of the pipe.

First surface 32 conforms to the shape of the wall of the pipe and in the embodiment described is thus arcuate. However, surface 32 may assume other shapes if other shaped members are to be held against movement. Slips 30 and 31 may be applied to the inside as well as the outside surface of tubular members, such as pipes, in which case the bowls would be disposed inside the pipes.

Slips 30 and 31, when bowls 19 are closed, encircle the pipes and loosely fit about the pipes so that the segments can move toward each other to grip the pipe as the compressive forces exerted by the screw clamp 22 and the wedging action increases.

Each of the segments 30a-30d and 3la-3ld of slips 30 and 31 also include a second surface 34 designed to engage the slip receiving bowls 19 and in such a manner that, when the pipe is moved in either direction along its length, the slip segments are moved toward the pipe thereby wedging the slip between the pipe and the bowls.

Referring to FIGS. 3A, 3B, and 3C which shows slips 31 in position between pipe 90 and bowl 20, second surface 34 includes a thick section 35 intermediate the length of the slip and is tapered from section 35 to ends 36 and 37 of the slip. Therefore the thickness of the slip is measured from the inside surface 32 to outside surface 34 varies axially from thick section 35 intermediate slip segments 3011-3011 and 31a-31d to ends 36 and 37 of the slip segments. This tapering forms two arcuate wedging areas 38 and 39 so that the slip will be wedged by the application of an axial force in either direction. In the embodiment disclosed arcuate wedging areas 38 and 39 are preferably unequal, the greater wedging area being area 39 which is for wedging in the direction of the greater force on the pipe. Of course, it is to be understood that these surfaces may be equal. In the utilization of slips 30 and 31 with hydraulic press 10, slips 30 hold pipe 90 against movement under large forces along its length applied in the direction of movement of support member 12 when hydraulic cylinders 14 are being retracted. When hydraulic cylinders 14 are being expanded it is only necessary that the holding force applied to the pipe in support member 11 be sufiicient to allow a mandrel or bell forming member to be removed from pipe 30, or to allow the slip to be returned to its normal position in bowls 19 and 20. Thus, the larger wedging area 39 ofslip 30 and its corresponding slip receiving surface in bowls l9 and 20 are arranged in support member 11 to oppose movement of the pipe in the direction of the greatest force.

Also, the arrangement of slip 31 and its corresponding bowl 20 in support member 12 is opposite to the arrangement described with respect to the slip and bowl of support member 11, because the greatest holding forces must be applied to the pipe held in support member 12 in the direction opposite to that applied to the pipe held in support member 11. Also, lesser holding forces need be applied by slip 31 when the mandrel is pulled from the pipe 30 or where the slips are being released from their wedging positions. Thus, in support member 12 slip 31 and the corresponding bowlmembers 19 and 20 have larger wedging areas 39 arranged to oppose the larger forces applied to move the pipe. Thus, the larger wedging areas 39 of slips 30 and 31 are on the outside end of support members 11 and 12 respectively, and the smaller wedging area 38 are opposite thereto. Also, in the embodiment described the degrees of the taper with respect to the first surface are equal.

Each of slip segments 30a-31d, preferably has two holes or slots 40 and 41 which in the embodiment described extend into the edges 35a of the thickest sections 35 in order to receive a cooperating pin 42. The hole 41 has a slightly smaller diameter than hole 40 so that hole 41 can retain the inserted pin 42 by interference fit for convenience in assembly. By the use of such cooperating pins and slots, the segments are restrained from axial movement with respect to each other.

Both upper slip receiving bowl groove 19a and the lower slip receiving bowl groove 200 have faces 50 and 51 forming a concave surface substantially complementing second surface 34 of the slips 30 and 30a. In other words, the diameter of the cylindrical opening formed by grooves 19a and 20a upper bowl 19 and lower bowl 200 is greater at the thicker section 35 of the slip. Faces 50 and 51 on bowl grooves 19a and 200 are complementary to the second surface, in that the concave faces taper parallel with the convex second surface of the slip from the point opposite thicker section 35 of the slip to the abuttments 52 and 53. Thus bowl groove face 51, which is larger in area than bowl groove face 50, receives wedging area 39 of the slip and thus the greater axial force exerted which occurs when pipe support 12 is moved toward pipe support 11 by the hydraulic cylinders 14. Conversely, wedging area 38 wedges against groove face 50 when movable pipe support 12 is moved away from stationary pipe support 11. Abuttments 52 and 53 serve to maintain the slips position when the upper bowl 19 is not clamped against lower bottom bowl 20, prevent the slips from being pulled out of the bowl when the pipe is removed, and make it easier to remove the pipe from the slips.

Another feature of this invention is the utilization of a bearing means between slips 30 and 31 and bowls 19 and 20 for aiding in alignment of the slips in the bowls. In FIGS. 2, 3A, 3B, and 3C a preferred form of the bearing means is disclosed as including a spherical ball 62 resiliently mounted by a spring 61 in a hole or opening 60 extending through the wall of each of bowls 19 and 20 adjacent the thickest section 35 of each of the slip segments. Spherical ball 62 which extends only partly through openings 60 and is urged against a lip 63 surrounding the end 60a of opening 60 adjacent the slips by coil spring 61 which abuts against ball 62. Spring 61 is compressed by a cylindrical cap 64 which may be inserted in opening 60 at the end 60b thereof opposite end 600. Cap 64 is maintained in position by a set screw 65. At least a portion of spherical ball 62 is received by a recess 70 at the intermediate thicker section 35 of second surface 34. The compression of spring 61 tends to maintain the ball 62 within recess 70 which operates to maintain the axial alignment of the slip. It is to be understood that these bearings and recesses may vary in number and may be located other than at the thickest portion of the slip.

As previously noted, one use of hydraulic press 10 is to forcefully join once piece of pipe (not shown) clamped in stationary pipe support 11 and another piece of pipe 90 in slidable support 12. Then using the hydraulic cylinder 14, movable pipe support 12 is forced toward stationary support 11 thereby forcefully telescoping the end of one pipe into the other pipe after the pipes are clamped against further axial movement by slips 30 and 31.

The operation of slips 30 and 31 are now described. Since the operation of each slip in conjunction with holding pipe is identical, only the placing of the slips and clamping of pipe 90 into movable pipe support 12 will be described. With upper slip receiving bowl 19 in the open position slip segments 31c, and 31d, connected to each other by pin 42, are placed in lower bowl groove 20a as shown in FIGS. 1 and 3a. Plates are fastened over the segments at the corners 71 of groove 20a to retain the slip segments in place. A similar procedure is followed in placing slip segments 31a and 31b in place in groove 19a of upper slip receiving bowl 20 of support member 12. One of segments 31a and 31b of the slip in upper bowl 19 and lower bowl 20 will have a pin 42 protruding from smaller hole 41 while the opposing segment in the lower and upper bowl, respectively, will have 'the larger hole 40, as shown in FIG. 2, to receive pin 42 when the bowls are clamped. Pipe is placed upon first surface 32 of slip segments 31c and 31d in the lower bowl groove 20a and upper bowl 19, with the slip segments in place, is closed, a section 81 of the upper bowl fitting under a nut 82 forming a part of screw clamp. Nut 82 is then rotated thereby clamping the pipe between the upper bowl 19 and the lower bowl 20 including the slip segment in the grooves 19a and 20a. As mentioned earlier, the same procedure is followed in clamping a second pipe in the stationary support 11. Thus the outer pipe walls now oppose surface 32 of slips 30 and 31 housed in the clamped upper and lower bowls. Screw clamps 22 are tightened so that the slip segments of each support member 11 and 12 are caused to frictionally grip the pipes with sufficient force so that when the pipes are moved along their length the slip 30 and 31 will tend to move with them into a wedging relationship with the walls of bowls 19 and 20.

Pistons 15 of hydraulic cylinders 14 are then retracted by introducing fluid into the piston end of cylinder 14 to move pipe support 12 toward pipe support 11. As the two pipes suported therein meet, an axial force equal to the force exerted by hydraulic cylinder 14 is directed against each pipe. As retraction of pistons 15 continues slips 30 and 31, tightly clamped to the pipes, are caused to move in opposite directions and after limited movement the slips become wedged between the pipe and the bowls and this wedging causes first surface 32 to be pressed against the pipe wall with sufficient force to frictionally bind the pipe against further movement with respect to the first surface of the Slip. Second surface area 39 of the slip is forced against complementary bowl faces 51 in a carnming relationship so that the slip is wedged between the bowl face and the pipe by the resistance of the tapered bowl faces to the axial force exerted by the tapered surface of the slip, thereby preventing any further movement of the pipe. However, unlike prior unitary slips, the pipe is not damaged by the large radial forces acting against the pipe because these are distributed from an area intermediate the slips toward the end of the slips.

Thus the slip actually moves slightly before attaining its wedged position; thereafter, the pipe is secure against the axial forces of the joining process. After the pipe is joined the upper bowls 19 may be unclamped thereby releasing the joined pipe from the slips.

After two pieces of pipe have been joined slips 30 and 31 will be tightly wedged between the pipes and bowls'l9 and 20. Also, as the slips move to the wedging position shown in FIG. 3B, ball 62 was depressed and the shoulder of recess 70 was forced against ball 62, as shown in this figure. The bias of spring 61 urges ball 62 against this shoulder and into recess 70 and if the slip is not too tightly wedged between the pipe and the bowl, this bias will return the slips to the position shown in FIG. 3A when screw clamp 22 is loosened. However, before it is possible to return the slips to the position of FIG. 3A it may be necessary to introduce fluid in the cylinder end of cylinder 14 and move piston 15 sufficiently to move support members 11 and 12 apart until the slips are loose enough to allow the biasof spring 61 to align the slips in the position of FIG. 3A. Screw clamp 22 and support member 12 can then be loosened and the slips 31 will be caused by the bias of spring 61 to take the position of FIG. 3A.

Also, the holding action of wedging areas 38 against the corresponding walls of bowls l9 and may be utilized to hold the pipe against movement when a bell forming member a mandrel (not shown) is removed therefrom. Since it is not necessary for the holding forces used in this instance, or where the slips are being unclamped, to be nearly so great as the holding forces applied to the pipe during the joining process, wedging areas38 may be smaller than wedging areas 39. In this case, as the direction of the movement of support member 12 is reversed by introducing fluid in the cylinder end of cylinder 14, the smaller wedging areas 38 are wedged between the pipe and bowls l9 and 20 of support member 12 as shown in FIG. 3C with sufficient force to tend to pull the mandrel from the pipe.

From the foregoing, it will be seen that this invention is one well adapted to attain all the ends and objects hereinabove set forth, together with other advantages which are obvious and or inherent to the apparatus.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.

As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or'shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

The invention having been described, what is claimed is:

l. A slip assembly for preventing axial movement of a member in either direction beyond wedged positions, comprising, in combination: a bowl having an inwardly tapered face; bearing means resiliently mounted in said bowl; and at least one double acting slip including a first surface for frictionally engaging said member to prevent movement of said member with respect to said first surface when the slip is in a wedged position, a second surface having an intermediate section and first and second wedging areas tapering from said intermediate section to the ends of the slip whereby the thickness of the slip is greatest at said intermediate section and decreases toward the ends, said second surface substantially complementing the face of said bowl, and said slip being disposed in said bowl so that axial movement of the member in either direction will cause the slip to be displaced until the slip is wedged between said member and said bowl to prevent further movement of said member, said second surface including a recessed area for receiving and cooperating with at least a portion of said bearing means so that alignment of said slip in said bowl will be maintained.

2. The assembly of claim 1, wherein the bowl includes an opening extending therethrough including a lip about one of its ends, and the bearing means includes a spherical ball disposed in the opening and extending partly through said one end and retained from passing from the opening through said one end by said lip, and further including a spring in the opening and abutted against said ball, and means inserted in the opening for causing said spring to be compressed to urge the ball against the lip.

3. The assembly of claim 2, wherein said last-mentioned means is a cylindrical cap inserted in the other end of said opening.

4. A hydraulic press for supporting two elongated members for movement under force toward or away from each other, comprising, in combination: two spaced apart rigid support members each including a double acting slip assembly in which one of said elongated members can be rigidly supported, each slip assembly including a bowl, and at least one double acting slip for limiting the movement of the elongated member supported therein in either direction along its length, each of said slips movable in its respective rigid support member between opposed wedged positions, and when such an elongated member is supported therein adapted to be wedged between one of said elongated members and its respective bowl in response to movement of such elongated member along its length, each of said slips having a first surface for frictionally engaging said elongated member to limit relative movement between said slip and such elongated member along the length thereof, and a second surface for engaging the respective bowl to impart movement of said slip toward such elongated member, thereby wedging only one end of said slip between such elongated memberand said bowl in response to engagement of said second surface with said bowl when such elongated member is moved in either direction along its length, while maintaining the other end of said slip relatively unwedged between such elongated member and said bowl, said second surface being tapered from each end to an intermediate thicker section of the slip whereby the thickness of the slip between said first and second surface varies axially from end to end, the thickest section being intermediate the ends of the slip; and motor means for moving one of said rigid support members toward and away from the other rigid support member.

5. The apparatus of claim 4, wherein each slip is comprised of a plurality of segments, each of said segments including cooperating pins and slots for restraining movement of said segments with respect to each other in said directions.

6. The apparatus of claim 4, where said elongated members are pipe and said first surface is arcuate, and said second surface is tapered inwardly from the thickest section to the ends of the slip to form two arcuate wedging areas so that the slip will be wedged by the application of axial forces to the pipe in either direction.

7. The apparatus of claim 6, wherein the degree of taper of each of the wedging areas is equal.

8. The apparatus of claim 6, wherein the wedging areas of the second surface are unequal.

9. The apparatus of claim 4, including a bearing means resiliently mounted in said bowl and a recessed area in said second surface for receiving and cooperating with at least a portion of a bearing means so that axial alignment of the slip and the bowls will be maintained.

10. The apparatus of claim 9 wherein the recessed area is in the intermediate thicker section of the slip.

11. A slip assembly for preventing axial movement of a member in either direction beyond positions in which a slip is wedged between such member and a bowl, comprising, in combination: a bowl having an inwardly tapered face; at least one double acting slip including a first surface for frictionally engaging said member to prevent movement of said member with respect to said first surface when the slip is in a wedged position, a second surface having an intermediate section and first and second wedging areas tapering from said intermediate section to the ends of the slip, the thickness of the slip being greatest at said intermediate section and decreasing toward the ends, said second surface substantially complementing the face of said bowl, and said slip being disposed in said bowl so that axial movement of the member in either direction will cause the slip to be displaced until the slip is wedged between said member and said bowl to prevent further movement of said member; bearing means resiliently mounted in one of said bowl or said second surface, and the other of said bowl or second surface including a recessed area for receiving and cooperating with at least a portion of said bearing means with a camming relationship so that said bearing means applies a force that urges said slip from said wedged positions.

I i i 1 

1. A slip assembly for preventing axial movement of a member in either direction beyond wedged positions, comprising, in combination: a bowl having an inwardly tapered face; bearing means resiliently mounted in said bowl; and at least one double acting slip including a first surface for frictionally engaging said member to prevent movement of said member with respect to said first surface when the slip is in a wedged position, a second surface having an intermediate section and first and second wedging areas tapering from said intermediate section to the ends of the slip whereby the thickness of the slip is greatest at said intermediate section and decreases toward the ends, said second surface substantially complementing the face of said bowl, and said slip being disposed in said bowl so that axial movement of the member in either direction will cause the slip to be displaced until the slip is wedged between said member and said bowl to prevent further movement of said member, said second surface including a recessed area for receiving and cooperating with at least a portion of said bearing means so that alignment of said slip in said bowl will be maintained.
 2. The assembly of claim 1, wherein the bowl includes an opening extending therethrough including a lip about one of its ends, and the bearing meaNs includes a spherical ball disposed in the opening and extending partly through said one end and retained from passing from the opening through said one end by said lip, and further including a spring in the opening and abutted against said ball, and means inserted in the opening for causing said spring to be compressed to urge the ball against the lip.
 3. The assembly of claim 2, wherein said last-mentioned means is a cylindrical cap inserted in the other end of said opening.
 4. A hydraulic press for supporting two elongated members for movement under force toward or away from each other, comprising, in combination: two spaced apart rigid support members each including a double acting slip assembly in which one of said elongated members can be rigidly supported, each slip assembly including a bowl, and at least one double acting slip for limiting the movement of the elongated member supported therein in either direction along its length, each of said slips movable in its respective rigid support member between opposed wedged positions, and when such an elongated member is supported therein adapted to be wedged between one of said elongated members and its respective bowl in response to movement of such elongated member along its length, each of said slips having a first surface for frictionally engaging said elongated member to limit relative movement between said slip and such elongated member along the length thereof, and a second surface for engaging the respective bowl to impart movement of said slip toward such elongated member, thereby wedging only one end of said slip between such elongated member and said bowl in response to engagement of said second surface with said bowl when such elongated member is moved in either direction along its length, while maintaining the other end of said slip relatively unwedged between such elongated member and said bowl, said second surface being tapered from each end to an intermediate thicker section of the slip whereby the thickness of the slip between said first and second surface varies axially from end to end, the thickest section being intermediate the ends of the slip; and motor means for moving one of said rigid support members toward and away from the other rigid support member.
 5. The apparatus of claim 4, wherein each slip is comprised of a plurality of segments, each of said segments including cooperating pins and slots for restraining movement of said segments with respect to each other in said directions.
 6. The apparatus of claim 4, where said elongated members are pipe and said first surface is arcuate, and said second surface is tapered inwardly from the thickest section to the ends of the slip to form two arcuate wedging areas so that the slip will be wedged by the application of axial forces to the pipe in either direction.
 7. The apparatus of claim 6, wherein the degree of taper of each of the wedging areas is equal.
 8. The apparatus of claim 6, wherein the wedging areas of the second surface are unequal.
 9. The apparatus of claim 4, including a bearing means resiliently mounted in said bowl and a recessed area in said second surface for receiving and cooperating with at least a portion of a bearing means so that axial alignment of the slip and the bowls will be maintained.
 10. The apparatus of claim 9 wherein the recessed area is in the intermediate thicker section of the slip.
 11. A slip assembly for preventing axial movement of a member in either direction beyond positions in which a slip is wedged between such member and a bowl, comprising, in combination: a bowl having an inwardly tapered face; at least one double acting slip including a first surface for frictionally engaging said member to prevent movement of said member with respect to said first surface when the slip is in a wedged position, a second surface having an intermediate section and first and second wedging areas tapering from said intermediate section to the ends of the slip, the thickness of the slip being Greatest at said intermediate section and decreasing toward the ends, said second surface substantially complementing the face of said bowl, and said slip being disposed in said bowl so that axial movement of the member in either direction will cause the slip to be displaced until the slip is wedged between said member and said bowl to prevent further movement of said member; bearing means resiliently mounted in one of said bowl or said second surface, and the other of said bowl or second surface including a recessed area for receiving and cooperating with at least a portion of said bearing means with a camming relationship so that said bearing means applies a force that urges said slip from said wedged positions. 